The present invention relates to concrete pipe reinforcing fabric and a method for forming concrete pipe reinforcing cages. Pipe reinforcing fabric comprises a network of a plurality of transverse wires and a plurality of line wires. When a cage is formed from the fabric, the transverse wires will correspond to the longitudinal wires in the cage while the line wires will correspond to the circumferential wires in the cage.
Traditionally, one purchases such fabric with the transverse wires arranged at 6, 8 or 12 inch intervals. This fabric can be used in forming cages of many different diameters. In forming a cage, the pipe producer cuts the fabric into the length needed to make a cage of a particular circumference. Length is determined by counting the transverse wires and thereby computing the desired length based on the known spacing between the transverse wires. Once the fabric is cut, it is formed into a circular or elliptical cage and the ends of the fabric are overlapped and secured together, typically by welding.
This procedure has been used in the industry for many years, in spite of the fact that it inherently results in wasted fabric. For example, in constructing a reinforcing cage for 12 inch diameter pipe, a cage is formed which is 14 inches in diameter and approximately 44 inches in circumference. The fabric used in forming such cages typically has transverse wires arranged at 6 inch intervals. In order to provide for the necessary 44 inches, the producer counts out eight transverse strands of wire and cuts the fabric generally adjacent the last strand. This results in fabric which is 48 inches long. Thus, the fabric must be overlapped 4 inches at the end in order to provide the desired 44 inch circumference. Since typically only one inch or so of overlap would be required in order to securely weld the cage, three inches of fabric are actually wasted.
Another difficulty which is encountered in this very popular prior art method is that the overlap must be gauged in order to insure proper circumference in the cage. The operator must take the time and trouble to set a gauge adjacent several circumferential strands as he overlaps and welds them. Thus, one encounters both wasted material and wasted time and energy in connection with the typical prior art method for forming conventionally available fabric.